Apparatus for internally coating cathode-ray tube envelopes



March 1952 P. w. CONWAY ET AL 2,589,054

APPARATUS FOR INTERNALLY COATING CATHODE-RAY TUBE ENVELOPES File'd Dec. 51, 1949 2 SHEETS SHEET l Relief Valve PHILIP W. CONWAY AND THADDEUS J. HAJDUK INVENTORS THETR ATTORNEY Cathode Ray Tube Envelope March 1952 P. w. CONWAY ET AL 2,589,054

APPARATUS FOR INTERNALLY COATING CATHODE-RAY TUBE ENVELOPES Filed Dec. 51, 1949 2 SHEETS-SHEET 2 Compressed A I r Solenoid Valve Air Line Turn Table PHILIP W. CONWAY AND THADDEUS J. HAJDUK INVENTORS THEIR ATTORNEY Patented Mar. 11, I952 UNITED STATES PATENT OFF ICE APPARATUS FOR INTERNALLY COATING CATHODE-RAY TUBE "ENVELOPES Application December 31, 1949, Serial No. 136,372

1 Claim. 1

This invention relates to apparatus utilized in the fabrication of cathode-ray tubes, and more particularly to improved apparatus for applying a conductive coating to the internal surface of a cathode-ray tube envelope.

When cathode-ray tubes are utilized in television receivers and the like, it has been found that the portion of the enclosing envelope in the vicinity of the electron beam becomes electrically charged and thereby affects the beam in a deleterious manner. In order .to prevent this, it is usual practice to coat the internal surface of this portion of the envelope with a conductive material which may have a suitable potential applied thereto to provide a field for focusing the electron beam projected towards a screen at one end of the enclosing envelope. This conductive material usually takes the form of a non-metallic, non-reflective colloidal graphite, known commercially as aquadag.

It is an object of the present invention to provide improved apparatus for applying a conductive coating to the internal surface of a portion of a cathode-ray tube envelope, which apparatus enables the coating process to be carried out quickly and economically, and in a highly simplified manner.

The features of this invention which are believed to be new are set forth with particularity in the appended claim. The invention itself, however, together with further objects and advantages thereof may best be understood by reference to the following description when taken in conjunction with the accompanying drawings, in which:

Figure 1 shows a schematic representation of the apparatus of the present invention,

Figure 2 shows a cathode-ray tube envelope to which an internal coating is to be applied,

Figure 3 shows one of the components of the apparatus,

Figure 4 shows a perspective view of the coating apparatus of the invention, and

Figure 5 shows a side view of the coating apparatus.

The apparatus illustrated in Figure 1 includes a pressure chamber I which, in turn, includes a vessel 2 containing a conductive graphite solution to be coated on the internal surface of a cathoderay tube envelope, such as indicated I3 in Figure 2. The pressure chamber I has removable top 3 which is mounted on the chamber in any known manner to form an air-tight enclosure within the chamber, and which may include a relief valve 24.

(Cl. 11811l Compressed air is forced into the pressure chamber I by means of an air line 4 which is connected to any suitable compressed air source (not shown), The air pressure applied to chamber I is indicated by .means .of a pressure gauge 5 and is regulated by means of a hand screw on a regulator 21 associated with the pressure gauge. A solenoid-operated valve 6 is also included in the line 4 to open and close this line upon actuation of the solenoid thereof in a manner well understood in the art. A filter 23 is included in line 4 to filter the air, and a hand valve 22 is also included to shut off the compressed air supply during the insertion of the vessel 2 in the pressure chamber I, and for periods when the apparatus is being cleaned.

The apparatus includes a brush mechanism for insertion into the small end of the envelope I3 of Figure 2 to apply the internal coating to the envelope. This mechanism includes a rod 1 having a handle portion 8 and a pivoted section 9. The section 9 is pivoted to a brush-holder Iii, this holder being spring-urged in a clockwise direction by a spring II. A brush I2 is mounted in the holder I 0., as shown more clearly in Figure 3. To enable the brush I2 to be manipulated within the cathode-ray tube envelope I3, the pivoted section 9 may be rotated about its pivot by a linkage mechanism which comprises a sliding arm I 4, anda link I5 coupling the arm I4 to the pivoted section 9.

The colloidal solution from the vessel 2 is supplied to the brush I2 by means of a tube I6 secured to the brush mechanism and extending from the holder I0 into the vessel 2. A pushbutton switch I! is mounted in the handle 8 and actuation of this switch closes an electrical circuit to the solenoid operated valve 6 for a potential source I8 through leads I9. The amount of air pressure in chamber I is controlled by regulator 2| and, as shown in Figure 3, the flow of the colloidal solution reaches the brush surface of brush I2 by means of an opening 20 along one side of the brush. As also shown in Figure 3, brush I2 is removable from holder III for cleaning purposes.

Figure 4 shows a perspective view of the coating apparatus. The apparatus includes a table 30 which supports the pressure chamber I. A back bracket 3| is fixed to table 30 and extends upwardly therefrom. The bracket 3| supports the air line 4 and its associated control elements 22, 6, 2 I, 5 and 23 in the manner illustrated. A turntable 32 may be obliquely supported by the bracket 3| and may be rotated by means of an electrical motor 40 (Figure 5) mounted on a sloping portion of the bracket 3| behind the turn-table. The turn-table 32 has a pair of fixed brackets 33 and pivoted bracket 34 mounted thereon.

As shown in Figure 5, the envelope l3 of Figure 3 may be removably supported on the turn table 32 by means of the brackets 33, 34, with its longitudinal axis aligned with the rotational axis of the turn table and with the face of its large end against the surface of the turn table. The pivoted bracket 34 is spring urged against the side of the envelope by means of a spring 35 to hold the envelope firmly in place.

To carry out the coating process, the envelope I3 is placed on and rotated with the tum-table 32. The regulator valve 2| is adjusted until a suitable operating pressure is indicated by the gauge 5 (for example 5 to 20 pounds per square inch depending upon the density of the colloidal solution in vessel 2). The brush [2 is inserted through the small end of the revolving envelope 13 (as shown in Figure 5) and switch I! is actuated to open valve 6 and supply air to chamber 1 by way of line 4. This increases the pressure in the chamber and forces the colloidal solution into line l6 and through this line to the surface of brush [2. The brush mechanism i manually manipulated by sliding arm [4 so that the brush I2 moves over the revolving internal surface of the portion of envelope [3 that is to be coated. When the coating operation is completed, the switch I! is released to close valve 6, out off the supply of compressed air to the pressure chamber I and interrupt the fiow of colloidal solution to the brush l2.

This invention provides, therefore, apparatus by means of which the conductive coating required on the internal surface of a cathode-ray tube envelope may be applied thereto in a rapid, accurate and highly simplified manner.

While a particular embodiment of the invention has been shown and described modifications may be made and it is intended in the appended claim to cover all such modifications as fall within the true spirit and scope of the invention.

We claim:

Apparatus for applying a coating solution to the internal surface of a vitreous envelope comprising: a pressure chamber containing said coating solution; an air line extending into said chamber for supplying compressed air thereto; an electrically operated valve in said air line for controlling the flow of compressed air to said chamber; a turn-table including means for removably supporting said envelope with its longitudinal axis aligned with the rotational axis of said turn-table for rotation of said envelope by said turn-table; a manually manipulable mechanism including, a support rod, a handle affixed to one end of said rod, a mechanical link pivoted to the other end of said rod for rotation with respect thereto, a brush fixed to the free end of said link for insertion into said rotatable envelope to apply said coating to said internal surface, and a slidable actuating arm extending parallel to said rod and coupled to said link for manipulating said brush; a further line extending from said chamber to said brush for supplying said solution to the surface thereof; and a switch mounted on said handle for actuating said electrically operated valve.

PHILIP W. CONWAY. THADDEUS J. I-IAJDUK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 502,414 Flower et al Aug. 1, 1893 1,254,429 Parmeley Jan. 22, 1918 1,704,364 Markley Mar. 5, 1929 1,882,576 Hannaford Oct. 11, 1932 1,999,014 Biggs et a1. Apr. 23, 1935 2,209,186 Briefer July 23, 1940 2,232,807 Scott Feb. 25, 1941 2,322,787 Brennan June 29, 1943 

